Agranulocytosis and antithyroid drugs

Propylthiouracil and methimazole are used widely in the treatment of hyperthyroid disorders. The most important complication of the use of these drugs is depression of the neutrophilic granulocyte count. Granulocytopenia occurs in about 4 percent and agranulocytosis occurs in about 0.3 percent of treated patients. Although this depression of the granulocyte count is reversible after the drug is discontinued, serious infection frequently accompanies agranulocytosis and accounts for almost all deaths related to the drugs. It is important to be aware of the clinical features of granulocytopenic reactions due to antithyroid drugs.

Agranulocytosis secondary to methimazole therapy: report of two cases

Seventy-three cases of thyrotoxicosis were treated at Lloyd Noland Hospital with methimazole, propylthiouracil or both. Two cases of agranulocytosis occurred (2.7%) secondary to methimazole. Both responded to hospitalization, reverse isolation, and antibiotic coverage with complete recovery of the peripheral blood picture. The toxicity of methimazole is noted. The need for careful monitoring of blood counts during therapy and immediate discontinuance of the drug at the first clinical sign of granulocytopenia is stressed.

[Drug therapy of hyperthyroidism]

The possibilities of the treatment of hyperthyroidism are mentioned, in which cases the author especially deals with the medicamentous therapy, taking into consideration the different chemical groups (imidazol derivations, thiourazil derivations, perchlorates) and their therapeutic mechanisms. The indications and contraindications of this treatment and the possible side effects are compiled in form of a table. The in-vitro-parameters which are necessary for the observation of the course are estimated in their significance. The author deals with the problems of the additional treatment. Taking into consideration indications and contraindications as well as controls of the course of functional parameters the medicamentous therapy concerned is a treatment with a good prognosis. It is promising particularly in such cases, when suitable parameters are used for the solution of the question concerning the end of the therapy. For this purpose nowadays two tests are at our disposal: 1. modified Alexander's test (radioiodine-test and suppression test under thyreostatic therapy) and 2. TRH-test with radioimmunological determination of TSH. The treatment should be carried out in adequate endocrinological dispensaries, as there are certain risks in not optimal therapy.

Immunological: reactions involving leukocytes: III. Agranulocytosis induced by antithyroid drugs

A method has previously been described which detected xenogeneic and allogeneic antibodies to human granulocytes by their inhibition of the normal phagocytosis-associated hexose monophosphate shunt (HMS) activity. This method was used to study three patients with acute agranulocytosis secondary to antithyroid drug administration. Two patients with methimazole and one patient with propylthiouracil induced agranulocytosis were studied. Serum samples from each of these three patients taken during the acute phase of agranulocytosis had inhibitory effects on phagocytosis-associated HMS activity in leukocytes from both normal donors and the patients after their full recovery from agranulocytosis. IgM but not IgG prepared from acute sera in two patients was also inhibitory. Disruption of IgM disulfide bonds by dithiothreitol destroyed its inhibitory activity. The possibility of drug-dependent immune destruction of leukocytes in these patients is discussed.

[Taste disorders and liver parenchymal damage after administration of thiamazole (author's transl)]

Marked, and in some cases long-lasting, taste disturbances occurred in three patients on thiamazole. In addition, all three had a rise in serum transaminases and alkaline phosphatase levels, due to associated liver parenchymal damage. Cause of these changes was the high thiamazole dosage (160 and 120 mg/d). Reduction in dosage restored normal taste sense in all three, but in two the drug had to be discontinued because of persisting high transaminase levels.

Treatment of hyperthyroidism in pregnancy with propylthiouracil and methimazole

Twenty-one women were studied who had received propylthiouracil or methimazole during 26 pregnancies. Four of the infants had a goiter at birth, and 3 of these had neonatal thyrotoxicosis. In 2 children neonatal thyrotoxicosis was not evident at birth because of maternal antithyroid therapy. Five children had congenital defects. Two mothers were responsible for 4 of the children with abnormalities, and both mothers had been treated with thiourea drugs for long periods, ranging from 7 to 11 years. The majority of children who are exposed to these drugs in utero appear to have no subsequent ill effects. However, prolonged therapy with these agents may be undesirable.